Cell mediated immunity was studied before and after surgery in patients with colorectal cancer. Thymus‐derived (T) lymphocytes were enumerated and their non‐specific activity was measured by assessing phytohaemagglutinin (PHA)‐induced blastogenesis. Specific T lymphocyte activity was measured by leucocyte migration inhibition in response to purified protein derivative of tuberculin (PPD) and autochthonous tumour extract. One group of patients received levamisole postoperatively and the other group consisted of controls. There was a more rapid return to preoperative levels of leucocyte migration inhibition to both antigens by the levamisole group. However, levamisole administration had only a marginal efect on the postoperative depression of cell counts and did not restore depressed lymphoblast transformation. Copyright © 1979 British Journal of Surgery Society Ltd.
